Propeller guard



Nov. 11; I952 J. DE BEURS 2,617,379

PROPELLER GUARD Filed July 19, 1947 INVENTOR JOMNNEs DE BEURS ATTOR NEYS Patented Nov. 11, 1952 Johannes de Beurs, Utrecht,Netherlands Application July 19, 1947, Serial No. 762,116 In the Netherlands May 20,1940

Section 1, Public Law 690, August 8, 1946. Patent expires May 20, 1960 2 Claims.

This invention relates to ships, and especially to ships having bow screws.

For difierent classes of the smaller menof war, such as torpedo boats and destroyers a high rate of speed is of vital importance in order to enable them to accomplish their tasks successfully. Since the speed of the targets to be attacked is steadily increasing, the rate of speed of the said ships must also be increased, in order to give them sufficient margin for attack, pursuit or retreat. It is, however, growing more and more difficult to attain this increased rate of speed, since the development of high rates of speed will, particularly in the case of the said small units give rise to various disturbing factors which will hamper the attainment of the increased rate of speed desired.

Some of the worst of the disturbing influences occurring when the ship has attained a high rate of speed may be reduced, if, besides the usual screws at the stern of the ship, there are also provided two or more screws at the bow. The known constructions provided with bow screws, however, show Various drawbacks.

For instance, some of these now known constructions show voluminous appendices at the bow, behind which the screws are located. Their greatest constructional disadvantage is the feature, that difiiculties will be experienced in the taking up of the thrust of the propelling force of the screws and the transmission thereof to the ship. The difliculties, from the viewpoint of navigation, reside, in this case, in the fact that the manoeuvring of the ship in port is greatly hampered, and in the danger to which the screws are exposed when the ship is lying at anchor, since these screws are entirely unprotected.

Another known construction shows means for the protection of the bow screws which is impractical, since it is very difiicult to use the anchors Without their dropping upon the said means and occasionally damaging the same.

With another known construction, the bow screws, the shaft bosses of which are secured to the hull by means of continuous members, are protected by means of screw protectors located at the same level as the screw shafts and consisting in straps bent arc-wise in front of the screws and secured to the bow of the ship. The present invention relates, generally, to a ship of this known type.

In the known construction an acute angle is formed between the shaft boss and the strap provided around the screw, which angle makes it necessary to provide a heavy horizontal plate above the screw, in order to prevent the anchor chainfrom getting caught in the said angle of the strap whereby it would get into the path of the screw.

This renders the construction too complicated and, moreover, will cause a great deal of resistance when the ship is runningat high rates of speed.

According to the present invention the said drawback is obviated by providing at the outside of the shaft boss a ridge extending towards the front along the screw and subsequently merging into a protective device located arc-wise in front of the screw, which device is secured to "the bow of the ship.

The said ridge has for its purpose to fill up the above mentioned acute angle, furthermore to protect the shaft-boss or tube, .and to provide a point of support towards the rear to the screw protector. The anchor chain is also kept clear of the ships hull by means of the said ridge, so that the screw cannot be damaged, no matter in what direction the anchor chain lies.

The construction thus formed is of a surprising efficiency, since the screw is sufliciently protected and .the whole will cause less resistance at high rates of speed than is the case with the known construction referred to above.

The invention will now be further explained with the aid of Figs. 1, 2 and .3 of the accompanying drawing.

In the said drawing:

Fig. 1 is a horizontal fore and aft section through the screw shaft in the bow of the ship;

Fig. 2 is a vertical cross section taken on line IIII in Fig. 1 through the foremost screw on the port side, the prow, and the screw protector being projected onto the plane of the main frame; while Fig. 3 is a fore and aft horizontal section, diagrammatically shown, through the screw shaft of the entire ship; and

Fig. 4 shows the assembly of shaft, shaft boss, and ridge.

The reference numeral 6 denotes the bow screws; l is the straplike screw protector; 2 is the ridge on the outer side of the shaft-bossing 3; which ridge merges towards the front into the screw protector l; 3 is the tubelike shaft-bossing, to the rear forming a swelling of the hull known as the shell bossing; 4 is the bracket-like bossing by means of which the shaft-bossing 3 is attached to the hull of the ship; 3 and 4 are known as the shaftbosses, or, in general, the bosses; 5 is the bow screw shaft; the stern screws being denoted by 1.

As the tubelike shaftbossing will run fairly clear from the hull for a considerable length along the bow, it will be necessary in this case to reinforce the bosses by several so-called spectacle frames (see Fig. 4) which in greater detail shows the device denoted by the reference numerals 2, 3, 4 and 5 in Fig. 1. The dimensions and curvature of the spectacle frames will be chosen in such a manner as to acquire the desired form of the bossing. The reference numeral 8 denotes the propeller shaft tube; 9 is the plane formed by the bosses 3 and 4 and. ridge 2; I0 is part of the hull at the bow; H is the angle enclosed by 9 and Ill.

The advantages of the present invention over the known constructions of this kind may be summarized as follows:

a. An eificient and adequate protection of the screws and of the shaft-bosses or tubes for the shafts.

b. A construction which will prevent to a considerable degree the rolling of the ship, and which most likely will render the provision of bilge keels superfluous, which in turn means considerable saving in weight and reduction of the resistance. For this purpose it may be advisable to mount the said construction on the hull of the ship at a greater or a lesser angle in accordance with the necessity of decreasing the rolling and pitching of the ship, see Fig. 4.

Furthermore the protection of the bow screws according to the present invention enables the successful performance of a so-called running, or flying moor, it thus being possible to anchor in all circumstances.

With larger ships the freeboard of the forebody can be correspondingly decreased as is generally the case with the stern, so that for this kind of ships the turtle-back shape can be realised.

The diameters of the screws can be chosen smaller if so desired.

It will be understood that this invention is susceptible to modification in order to adapt it to different usages and conditions, and, accordingly, it is desired to comprehend such modifications within this invention as may fall within the scope of the appended claims.

In the case of electric transmission of the power to the bow-screws this transmission requires only a small space.

Iclaim:

1. In a vessel having a hull tapering inwardly at the bow end; said hull being formed with a shoulder on each side adjacent the bow end substantially normal to the axis of the hull and facing the said bow end, a propeller shaft projecting from inside the hull out through each said shoulder in substantially a fore and aft direction, each shaft ending short of the end of the hull and being spaced from the side of the hull externally thereof forwardly of said shoulders, a propeller on the outboard end of each said shaft, a tubular shaft boss surrounding each shaft between the said shoulder and propeller pertaining thereto, each shaft boss having rigid therewith flat fin members on opposite sides thereof, one of said members being between the shaft boss and hull and also being connected with the latter whereby rigidly to support the shaft boss relative to the hull, and the other of said mem bers tapering outwardly from the hull end of the shaft boss to a point rearwardly of the propeller and outwardly from the periphery thereof, and an arched strap formed with the outer edge of the said other of said members extending across in front of the propeller and connected at the other end to the hull.

2. An arrangement according to the preceding claim wherein the said fin members and straps are coplanar with each other and with the axis of the shaft in the associated shaft boss.

JOHANNES DE BEURS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 903,592 Low Nov. 10, 1908 1,294,082 Golden Feb. 11, 1919 1,302,982 Shonnard May 6, 1919 1,360,036 Shonnard Nov. 23, 1920 FOREIGN PATENTS Number Country Date 7,291 Great Britain May 6, 1884 366,265 France Oct. 1, 1906 

